diff --git a/lib/dotenv/diff.rb b/lib/dotenv/diff.rb
index 329473b..0085c40 100644
--- a/lib/dotenv/diff.rb
+++ b/lib/dotenv/diff.rb
@@ -50,7 +50,10 @@ def any?
     private
 
     def snapshot
-      ENV.to_h.freeze
+      # `dup` should not be required here, but some people use `stub_const` to replace ENV with
+      # a `Hash`. This ensures that we get a frozen copy of that instead of freezing the original.
+      # https://github.com/bkeepers/dotenv/issues/482
+      ENV.to_h.dup.freeze
     end
   end
 end
diff --git a/spec/dotenv_spec.rb b/spec/dotenv_spec.rb
index 08e7cb9..363a10c 100644
--- a/spec/dotenv_spec.rb
+++ b/spec/dotenv_spec.rb
@@ -336,6 +336,15 @@
       Dotenv.instance_variable_set(:@diff, nil)
       expect { Dotenv.restore }.not_to raise_error
     end
+
+    it "can save and restore stubbed ENV" do
+      stub_const("ENV", ENV.to_h.merge("STUBBED" => "1"))
+      Dotenv.save
+      ENV["MODIFIED"] = "1"
+      Dotenv.restore
+      expect(ENV["STUBBED"]).to eq("1")
+      expect(ENV["MODIFED"]).to be(nil)
+    end
   end
 
   describe "modify" do